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DTC P0125: Closed Loop Temp Not Reached: Testing

NOTE: To diagnose this DTC, manufacturer recommends allowing vehicle to sit overnight in order to have a totally cold engine. If any ECT sensor DTCs are present, repair those DTCs before continuing with this test. Extremely cold outside ambient temperatures may have caused this DTC to set.
  1. Turn ignition on. Using scan tool, read DTCs. If GOOD TRIP counter for DTC P0125 is displayed and displayed count is "0", go to next step. If GOOD TRIP counter for DTC P0125 is not displayed or displayed count is not "0", go to step  6 .
  2. Ensure coolant level is in good condition and at proper level. Replace or top off coolant as necessary. If coolant is okay, go to next step.
  3. Turn ignition on. Using scan tool, read ENG COOLANT TPM DEG value. If engine was allowed to sit overnight, scan tool temperature value should be near ambient air temperature. If engine coolant temperature is more than 180°F (82°C), allow engine coolant temperature to cool down to 150°F (66°C) before proceeding. If engine coolant temperature is 150°F (65°C) or less, start engine. Using scan tool, monitor ENG COOLANT TPM DEG until engine coolant temperature reaches 180°F (82°C). Temperature value should increase smoothly from start-up to normal operating temperature. Also monitor actual coolant temperature with a thermometer. As engine warms up to normal operating temperature, actual coolant temperature should be relatively close to temperature reading on scan tool. Monitor coolant temperature and note when thermostat opens. Thermostat should open at about 195°F (90°C). Replace thermostat as necessary. If thermostat opens as specified, go to next step.
  4. If coolant temperature increased smoothly, no problem is indicated at this time. Test is complete. If temperature did not increase smoothly, turn ignition off. Disconnect PCM connectors. PCM is located on firewall in right rear corner of engine compartment. Visually inspect connectors for corroded, damaged, pushed-out or miswired terminals. Repair connectors as necessary. If connectors are okay, go to next step.
  5. Disconnect ECT sensor connector. See Figure . Visually inspect connector for corroded, damaged, pushed-out or miswired terminals. Repair connector as necessary. If connector is okay, replace ECT sensor.
  6. Turn ignition off. Visually inspect related connectors and wiring harness for damage. Repair connectors and wiring harness as necessary. If connectors and wiring harness are okay, reconnect all connectors. Start engine. Wiggle ECT sensor connector and wiring harness while monitoring scan tool display. If GOOD TRIP counter display count changes to "0", repair connector or wiring harness where wiggling caused display to change. If GOOD TRIP counter display count does not change to "0", no problem is indicated at this time. Check for any related technical service bulletins that may apply.
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